precursor amino acids, as a result of the action of either endogenous amino acid decarboxylase activity (Halasz et al., 1994) or by the growth of decarbox-
ylase positive microorganisms (Halasz et al., 1994;
Silla Santos, 1996). The low pH (below 4.5 after 2
days of fermentation) and the physical characteristics
of fish silage that lead to a low oxygen concentration
within the ensiled fish are favourable for the action
of amino acid decarboxylases (Beutling, 1992).
Thus, biogenic amines may pose a potential risk in
fish silage. These compounds are toxic for livestock,
causing liver damage and decreasing the perform-
ance of the animals (Krizek, 1991). In susceptible
humans, they can lead to a variety of cutaneous,
gastrointestinal, haemodynamic and neurological
symptoms (Taylor, 1986).
Biogenic amines can be degraded by amine oxid-
ases. Diamines, such as histamine and putrescine, are
degraded by diamine oxidase (DAO). The activity of
these enzymes is maximum under neutral to alkaline
conditions, and oxygen is necessary for their action
(Beutling, 1992). DAO can provide a means of
controlling histamine accumulation during the first
days of ensilage, while the pH is high enough and
some oxygen is still available within the product.
Little is known about histamine degradation by LAB,
but Voigt and Eitenmiller (1978) and Leuschner et
al. (1998) found DAO activity among some dairy
and meat isolates, respectively.